A presence service is also referred to an existence service, which is a communication service for collecting and distributing presence information. At present, the presence service is usually provided together with an instant message service. Of course, the presence service may also be provided independently, or in conjunction with other services, such as network game services. Further, standard specifications related to presence services have been worked out preliminarily by international standard organizations such as OMA (Open Mobile Alliance), and are now being perfected continually.
The presence service mainly relates to three components: a presentity, presence information and a watcher. The presentity may be a natural person, or a non-natural person. In addition to basic information of a presentity such as online/offline state and communication mode, the presence information may also include extended information such as mood, location, activity, and value-added service information provided by the non-natural person, such as information of weather forecast, station or television program and traffic movement. The watcher, i.e., a receiver of the presence information, may be the natural person or the non-natural person.
In a data model of the presence information provided by IETF (Internet Engineering Task Force), the presence information is divided into three parts as shown in FIG. 1, including: Person, Service and Device. The specific elements corresponding to the above three parts in a presence information document are as follows: <person> element, <tuple> element and <device> element. Each of the three elements includes a great number of sub-elements. For example, <person> element may include sub-elements such as <activities>, <mood>, <status-icon> and <time-offset>. For detail, reference may be made to corresponding standard specifications of IETF or OMA.
A method for realizing a presence service in the prior art mainly includes the following issuing presence information by a presentity, receiving and storing the presence information by a presence server, and determining, by the presence server, the presence information that is allowed to be obtained by the watcher according to an authentication configuration information, distributing, by the presence server, the presence information to a corresponding watcher, and presenting received presence information by the watcher.